Agriculture Reference
In-Depth Information
12
EC
PM-sc
PM-ref,out
Irrigation
10
8
6
4
2
0
158
159
160
161
162
163
164
165
166
167
168
169
170
171
DOY (2005)
Fig. 10.15
Total daily evapotranspiration as measured by the Eddy Covariance technique (
black
bars
) and estimated by two models.
PM-sc
: screenhouse evapotranspiration model (
gray bars
);
PM-ref, out
—reference evapotranspiration for external conditions (
empty bars
). The
dashed hori-
zontal line
is the irrigation supplied by the grower.
JD
: Julian Day. (Source: Tanny et al.
2012
)
To model ET accurately in screenhouses, Möller et al. (2004) suggested a modi-
fied Penman-Monteith model which includes an additional boundary layer resis-
tance due to the boundary layer occupying the air gap between the canopy top and
the screen. They measured transpiration of pepper plants in an insect-proof screen-
house, using sap flow and eddy covariance techniques; they found good agreement
between the two measurement approaches and between the measurements and the
newly derived model.
In a study conducted in a large banana screenhouse near the Sea of Galilee
in northern Israel, ET was measured by an eddy covariance system (Tanny et al.
2006
) and the measurements were compared with two types of models; the Pen-
man-Monteith model of ET0 (Allen et al.
1998
) under external meteorological
conditions, and the modified ET model for internal screenhouse conditions. Fig-
ure
10.15
presents the results of measurements over a period of 14 days in June
2005. The results show that the screenhouse model is somewhat lower than the
measurements. The model for ET0 is significantly higher however, illustrating
the effect of the screenhouse in reducing ET. The results of Fig.
10.15
show that
irrigation (dashed horizontal line) was consistently higher than the actual crop
water use. Note that this irrigation level was already about 70 % of the irrigation
supplied to open banana plantations in this region and that although irrigation
was increased from JD (Julian day) 166, actual crop water consumption did not
change suggesting the possibility of water savings.
